“I Can’t Think Straight,” novelist/filmmaker Shamim Sharif’s lesbian romantic comedy, offers a lamely feel-good mix of the familiar and the exotic (female polo players, anyone?). Comely leads Lisa Ray and Sheetal Sheth (the Sapphic couple in Sharif’s “The World Unseen”) nearly generate enough hot-blooded believability to temper the blatant over-simplications in this London-set cross-cultural love story. But the film is too schematic by half and overflows with one-dimensional characters; Sharif lacks the snap-timed comic variations to make repetition funny. Pic, which bows Nov. 21 at Gotham’s Quad Cinema, could do OK in ancillary.

Though it’s being released two weeks after “The World Unseen” Stateside, “I Can’t Think Straight” actually reps Sharif’s first venture as director, refinancing problems having delayed the film’s completion. In both cases, Sharif’s novels have suffered in translation to the screen, with detail and subtlety sacrificed to point-making exposition and broad caricature.

One camera pan around Leyla’s bedroom, ending on a k.d. lang CD, is enough to clue her sister Yasmin (Amber Rose Revah) in to her still-undeclared sexual preferences, while Tala’s egotistical informer of a sibling (Anya Lahiri) turns out to be an elegant chip off the old Cruella-esque maternal block.

Leyla and Tala themselves are a study in contrasts. Shy, budding novelist Leyla dutifully toils away at Daddy’s insurance firm, while Tala, irony intact, strides confidently through her privileged jet-set world, leaving her family to prepare for her latest projected nuptials (Tala’s fourth fiance having lasted slightly longer than the previous three) amid an endless parade of foods and fabrics.

The overwhelming attraction that sparks between Leyla and Tala builds from fierce tennis matches to dreamy strolls through Oxford to tastefully passionate bedroom clinches. The relationship liberates timid Leyla, who comes out with a vengeance, while hitherto fearless Tala briefly retreats into heterosexual traditionalism — at least until the morning of her fourth would-be wedding.